The present invention relates to a one step process for preparing a 1,3-diol, and 1,3-propanediol in particular.
1,3-Diols have plenty of uses, particularly in the synthesis of polymers. For instance, xe2x80x9cCORTERRAxe2x80x9d (trademark) is a polyester made of 1,3-propanediol (hereinafter xe2x80x98PDOxe2x80x99) and terephthalic acid, which polymer has outstanding properties. Other 1,3-diols may find similar use. Commercially attractive routes to prepare such 1,3-diols are therefore highly desirable.
U.S. Pat. No. 5,304,691 and the art described therein relates to a process for making PDO and HPA (3-hydroxypropanal, a 3-hydroxyaldehyde). In this particular patent, PDO and HPA are made by intimately contacting an oxirane (ethylene oxide, hereinafter xe2x80x98EOxe2x80x99), a ditertiary phosphine-modified cobalt carbonyl catalyst, a ruthenium catalyst promoter, and syngas (carbon monoxide and hydrogen) in an inert reaction solvent at hydroformylation reaction conditions. A PDO yield of up to 86-87 mole % is reported, using a catalyst comprising cobalt ligated with 1,2-bis(9-phosphabicyclononyl)ethane as bidentate ligand, and either triruthenium(0) dodecarbonyl or bis[ruthenium tricarbonyl dichloride] as cocatalyst.
As mentioned, this process typically results in the synthesis of a mixture of HPA and PDO. However, it would be much more attractive to produce PDO in a single step, or in a higher yield, obviously without co-producing impurities that inhibit the use of PDO in the preparation of polymers etc. In order for this process to be particularly successful, recycle of the catalyst without significant deterioration of performance is needed. Surprisingly such a process, and a catalyst suitably used therein has now been found.
Accordingly the invention provides a process for an improved oxirane hydroformylation catalyst, the improved oxirane hydroformylation catalyst, and a one step process for preparing a 1,3-diol in the presence of such a catalyst where recovery of product is preferably accomplished via phase separation of a diol rich phase from the bulk reaction liquor.
The process for preparing an improved oxirane hydroformylation catalyst involves:
a) forming a complex (A) by contacting a ruthenium(0) compound with a ditertiary phosphine ligand; and
b) forming a complex (B) by subjecting complex (A) to a redox reaction with a cobalt(0) carbonyl compound.
The novel oxirane hydroformylation catalyst involves complex (B), which is postulated to be a ruthenium(+1)-phosphine bidentate:cobalt (xe2x88x921) complex. The characterizing feature of the novel catalyst is that the metal being ligated is ruthenium rather than cobalt as in the ""691 US patent referred to above. Indeed, upon analysis of both systems a distinct difference in the catalysts was noted in the IR spectra. The IR spectrum of the catalyst according to the present invention revealed the presence of phosphorus-ruthenium bands at 2107, 2053, and 2040 cmxe2x88x921, which are not present in the IR spectrum of the catalyst according to the invention of the ""691 patent.
Finally, the invention also provides a one step process for preparing a 1,3-diol, comprising the reaction of an oxirane with syngas at hydroformylation conditions in an inert solvent in the presence complex (B) as catalyst.